In the past, the sheeting used as surface covering for dashboards in motor vehicles has been manufactured from polyvinyl chloride. The chlorine content and heavy metal components included in such polyvinyl chloride molding compounds have caused recycling problems. In automotive applications `fogging`, that is outgassing of plasticizer or softening agents is known to occur when such sheeting is exposed to solar radiation. The outgassed material may collect and become noticeable as a troublesome film on the inside of a vehicle's windshield.
Commercially available thermoplastic polyurethanes, used in the manufacture of artificial leather and in extrusion and injection molding processes, are in fact suitable for thermoplastic processing in Sinter-Powder-Methods; however, they do not completely fulfill the requirements of the automotive industry for dashboard soft trim, particularly with respect to light and temperature stability.
Aromatic diisocyanate components in aromatic thermoplastic polyurethanes are not light-resistant and can, upon exposure to light, cause considerable yellowing in lighter shade materials and even a change in color intensity and luster in black materials.
While aliphatic thermoplastic polyurethanes may be light-resistant, their temperature stability may not be sufficient for motor vehicle dashboard applications. The interior space behind the windshield in a motor vehicle can heat up to over 100.degree. C. when exposed to strong solar rays. Such high temperatures are above the softening point of typical aliphatic thermoplastic polyurethanes. Accordingly, grain stability (grain crack resistance) up to a temperature of 130.degree. C. and hot-light stability up to 120.degree. C. may not be attainable with a conventional aliphatic thermoplastic polyurethanes.